Tuesday 31 May 2011 10.59 EDT
First published on Tuesday 31 May 2011 10.59 EDT

Steve Jobs is to take to the stage at Apple's Worldwide Developer Conference in San Francisco next week to launch the next generation of Apple's mobile software, iOS 5, the company has confirmed.

The appearance will only be Jobs's second public one this year. In January, he announced that he was taking medical leave from the company for unspecified reasons – though they are believed to be complications arising from his surgery in 2004 to remove a neuroendocrine tumour from his pancreas.

In a rare advance announcement, Apple confirmed WWDC's key software announcements with iOS 5, the next version of its iPhone operating system, due to preview alongside Mac OS X 10.7 Lion, the eighth version of the Mac OS operating system. (Eighth? Because it started at 10.0.0 in March 2001.) Both were widely expected and will be detailed in the keynote speech led by Jobs and "senior Apple executives" – expected to include head of marketing Phil Schiller and Scott Forstall, head of iOS development.

Apple also confirmed that it will unveil "iCloud", which it described as its "cloud services" offering. Given that Apple already offers some of those services through its MobileMe paid subscription product - including calendars, email, web hosting and file storage – there will be intense interest around iCloud.

The expectation is that it will effectively upgrade iTunes, allowing users to stream music directly to their devices. Apple has reportedly signed three of the four major music labels, with Universal close to signing.

That would be a riposte to Google and Amazon, which have unveiled cloud music services that reviewers have so far been underwhelmed by. Amazon in particular did not get any licensing from music labels – meaning that people can only stream music that they have either bought or uploaded to the service. The expectation is that iCloud may allow users to stream any song that they already own, an echo of Michael Robertson's plans implemented in the 1990s at MP3.com. That was shut down by lawsuits from the record companies.

• Lion is expected to include improvements to Apple Mail, Finder and iCal, a "reading list" and "Mission Control" and the introduction of some successful user interface features from the iPad, such as more semi-transparent windows for less important elements such as downloads in progress on a browser. The mention of iCloud could also indicate a move to include a feature not unlike cloud-based file storage service Dropbox.

Other elements introduced by Lion include the ability to resize windows by dragging any part of the edge – something Windows users have been used to for decades.

• iOS 5 is expected to integrate further with Lion, and offer new "widgets" that will display custom information on the device's home screen – a response to Google's lead in providing "notifications" (about arriving emails, statuses, messages and so on) on Android. While iOS has a substantial lead in developers and app downloads over Android, the rapid evolution of Google's product has left a number of influential users calling for a better notification system than the passive "updated icon with a number" or active "modal dialog" which blocks other activities. Apple last June hired Rich Dellinger, who designed the notification system for Palm's webOS, away from that company and back to the company where he worked between 1999 and 2006. The expectation is that his input will be crucial to iOS 5.

• One more thing? As always, the rumours that Jobs will reveal some extra bit of hardware to wow the crowd persist. Some are suggesting a refresh of the MacBook Air; others have not given up hope of seeing the iPhone 5 (or 4S, or 4G). A report in the International Business Times labelled the next iPhone as iPhone 4S with a faster processor and 8-megapixel camera, as well as compatibility with both GSM and CDMA networks.